Research on the Control Strategy of a Three-Level Back-To-Back Converter with a Vienna Rectifier as the Front-End Stage

This paper focuses on a unidirectional three-level back-to-back converter with a Vienna rectifier as the front-end stage. A coordinated control strategy is proposed to address the issues of grid-side current zero-crossing distortion (CZCD) and neutral-point potential (NPP) imbalance. The proposed strategy mitigates CZCD by compensating reactive current in the Vienna rectifier. Meanwhile, considering the coupling between zero-sequence voltage (ZSV) injection and CZCD in the Vienna stage, a coordinated neutral-point potential (CNPP) control strategy is developed. This method reconstructs the neutral-point current reference and achieves NPP balance by optimizing ZSV injection on the inverter side. The effectiveness of the control strategy is validated through simulation and experimental results.